1. Field of the Invention
The present invention relates, generally, to cell connectors for insuring direct electrical communication and positive mechanical connection with a cell in a bipolar permselective membrane electrolyzer, while precluding fluid and gaseous flow therefrom. More particularly, the present invention relates to an intercell connector for bipolar permselective membrane electrolyzers utilized for the electrolysis of sodium chloride brine in the production of chlorine and caustic soda.
2. Description of the Prior Art
The electrolysis of sodium chloride brine is by far the most important commercial process for producing chlorine and caustic soda. Recently, there has been tremendous commercial interest in electrolysis cells incorporating metallic anodes, rather than graphite anodes used theretofore, for this process. Further along these lines, there is evolving a clear trend toward the use of cationic permselective membranes, and away from the formerly conventional permeable deposited asbestos diaphragms employed in these cells. The permselective membranes differ substantially in nature from the permeable diaphragms in that no hydraulic flow from anode to cathode compartments is permitted. The permselective membranes, typically ion exchange resins cast in the form of a very thin sheet, consist of a perfluorinated organic polymer matrix to which ionogenic sulfonate groups are attached. Thus, during electrolysis of sodium chloride brine, the negatively charged groups permit transference of current-carrying sodium ions across the membrane while excluding chloride ions. Consequently, it is now possible to produce caustic soda of a predetermined concentration, and one nearly free of chloride, within the cathode compartment due to these ionic constraints imposed upon the system.
Maximum utility of a system incorporating metallic anodes and permselective membranes is achieved by a multi-cell design wherein cells are arranged in serial fashion. While such a design takes full advantage of the characteristics of these bipolar, permselective membrane electrolyzers, a particularly troublesome problem arises in effectively providing direct electrical communication and positive mechanical connection between the various cells, as well as to the external source of electrical power employed for electrolysis. That is, while the membrane itself does not permit gross hydraulic flow between the various compartments, the art has encountered substantial difficulties in minimizing fluid and/or gaseous flow between compartments at the various intercell connection locations.
Certain cell and intercell connectors have been proposed to minimize the leakage problem from or between cells while yet insuring good mechanical and electrical contact. These connectors routinely incorporate sealing devices including gaskets, O-rings, and the like. See, for example, U.S. Pat. Nos. 3,752,757, 3,788,966, 3,824,173, 3,902,985, 3,915,833, 3,950,239, and 3,970,539. However, it is found that those devices which maximize mechanical connection with an eye toward minimizing fluid or gaseous leakage between cells often sacrifice optimum electrical communication. On the other hand, those devices maximizing electrical communication are found to be less than totally efficient in minimizing fluid and/or gaseous leakage, due to, for example, corrosive degradation of the components or inherent design problems.
Accordingly, the need exists to provide a cell connector, particularly an intercell connector, for a bipolar permselective membrane electrolyzer which maximizes both mechanical connection and electrical communication between the cells while substantially precluding fluid and/or gaseous flow.